As is known, in variable-geometry turbines, the stator blades can be rotated about respective axes to adjust the gas flow section in the nozzles defined by the blades, and so improve turbine efficiency over a relatively wide range of operating conditions.
More specifically, the stator comprises two annular platforms defining a conduit, along which the gas flows, and which houses the airfoil profiles of the blades. Each airfoil profile is hinged to the two stator platforms, and comprises a tail portion defined radially, with respect to the turbine axis, by two end walls fitted in sliding manner to the platforms.
Given the high temperature of the gas conducted by the turbine, particularly in aircraft applications, the connecting regions between the moving parts of the blades and the fixed parts of the stator must be cooled by streams of cooling air to prevent jamming of the blades and ensure accurate gas flow adjustment. More specifically, a need is felt to cool said end walls and improve heat exchange efficiency to minimize the amount of cooling air required.